Enhancing the activity and stability of zeolite catalysts for industrial applications related to hydrocarbon upgrading (e.g., cracking, C1 chemistry, etc.) is often related to the development of new synthesis protocols that produce nano-sized or hierarchical materials with reduced internal molecular diffusion constraints. Zeolite structures possess inherent confined pore networks that confer shape-selectivity, yielding highly specific products, albeit often with diminished activity and lifetime. For instance, zeolites featuring one-dimensional pores like MTW exhibit heightened propylene selectivity in alkane cracking but faster deactivation due to extensive coking and pore blockage. One viable solution that will be discussed in this presentation involves a straightforward post-synthesis treatment to generate fins, which are ultrasmall protrusions that epitaxially grow from the surfaces of seed crystals. This secondary growth method has been successfully applied to zeolites with both three-dimensional (e.g., MFI, MEL) and two-dimensional (e.g., FER) pore networks, resulting in faster molecular diffusion and, thus, reduced coking rates and prolonged catalyst stability. Here we will describe our recent efforts to design finned one-dimensional zeolites: MOR, MTW, MTT, and LTL. These finned materials exhibit superior mass transport properties, as demonstrated by diffusion measurements with several probe molecules, including 2-3-dimethylbutane, p-xylene, and n-hexane. Catalytic testing of seeds and finned counterparts reveal that latter exhibit improved turnovers, olefin selectivity, and lower deactivation rates in the methanol to hydrocarbons (MTH) reaction. Moreover, the finned materials outperform conventional catalysts in n-hexane cracking, with olefin selectivity comparable to commercial ZSM-5 zeolites. In this presentation, we will discuss the different types of fins produced on 1D zeolites based on differences in seed crystal anisotropy. We observe that morphological distinctions in secondary growth result in intriguing variations in structure-performance relationship compared to prior findings for other (2D and 3D) finned zeolites.
